2000 Saturn SC2 Power Loss from stop and going up hill.

Ever since 'shady' mechanic replaced "throttle control valve" and a "temperature sensor" on my engine, I have loss of power. My car tries to shift gears while going up hills and I feel the car begin to shift as I see RPM's waver a tad lower but then the "pull" kicks in like I let off the gas (but I haven't!) And then the RPM's rev back up a couple seconds later until it finally does shift. Only up hills did I receive this problem. Also car is very slow to start accelerating from a dead stop. Took to a wonderful GMC dealership who's very attentive to what I'm trying to achieve. I had previously (less than 9 mos ago) replaced fuel pump/fuel filter with the previous "shady" guys. This GMC dealership has sense replaced my first catalytic converter which allowed me to feel more power from a dead stop however shifting problem still there. Dealer's tech, mechanic and spouse all say they can't tell but none of them have taken it up the hills I do on my way to work- giving it the power I typically have for years. I am sole owner of this car and know all that's been done to it- I don't trust this "shady" mechanic who may have not put good parts on my car. I see all these problems resulting in same thing. Fuel pump/fuel filter etc. I really need to know before I pay for one again if that's a problem. Husband says it's my "kickdown cable" but I can't find one on my car via any diagrams I see. Odd that it tries to shift and doesn't at first, but then finally kicks in w/out pushing down on gas pedal any farther.